Polydimethylsiloxane (PDMS) molds have been widely used in soft lithography, specifically for making stamps for micro-contact printing (μCP) and soft micro-molding processes. DOW CORNING® SYLGARD® 184 is the most common mold making material for these applications. PDMS offers several desirable properties, such as elasticity, conformal contact, low surface energy, good surface release, and transparency. In a pattern transfer technique, such as roll printing or μCP process, the use of polar inks can create issues of incompatibility between the ink and the hydrophobic PDMS mold surface. In micro-molding processes, solvent based polymers are used as printing media, and PDMS based molds have only limited permeability to the more polar solvents.
For applications that require patterning of polar solvent-based polymer films followed by solvent removal in the mold, the solvent diffusion rate of PDMS may not be sufficiently practical. This is largely attributed to the non-polar nature of PDMS. A typical method to increase the polarity of a PDMS mold is to treat the surface with an oxygen based plasma. However it is known in art that the induced surface hydrophilicity is not permanent and will disappear in a few hours. A number of organic hydrophilic elastomer molds have been reported to work with polar inks for μCP. The use of organic molds has not been as widely accepted as PDMS molds. Pattern transfer has been successfully demonstrated on solvent based polymer films using modified PDMS molds. Solvent removal from under the mold is a critical factor in the patterning step. It is desirable to have a high solvent diffusion rate or high solvent adsorption in the mold to enhance solvent removal for successful pattern transfer.